The U.S. Government has developed a Global Positioning System (GPS). The GPS consists of a number of GPS satellites. A GPS receiver receives signals from the receivers and determines the terrestrial position of the GPS receiver.
The GPS satellite signals are processed by the GPS receiver using triangulation techniques in order to estimate the position of the receiver. Commercial GPS receivers have position estimate accuracies of .+-.100 meters.
One solution to obtaining more accurate position estimates is Differential GPS. Differential GPS utilizes a reference station in order to improve accuracy. The reference station is equipped with a GPS receiver known as a Differential GPS receiver. The Differential GPS receiver produces correction signals in response to the signals received from the GPS satellites. The correction signals and/or other reference station information are transmitted to the GPS receiver at the user location and are used to improve the accuracy of the user position estimates.
Typically, the reference station is located at a central, fixed location. However, a particular work site may contain locations where a fixed, permanent reference station is not practical or where communication signals from the reference station cannot be received.
The present invention is aimed at one or more of the problems identified above.